I am a super-mod for https://www.speedrun.com/it_takes_two, and we have a "Solo Co-op" category, but we don't need the "Online" and "Local" variables in that Solo Co-op category. Do i have to manually set the variables to be everything except for "solo Co-op" or is there a way i can get around that?

Sadly, what you described indeed requires a separate variable for each category. There is no other way to overcome the "one or all" property of the variable.

Elo mentioned changes to this mechanic when the improved moderator tools will come out, but there is no ETA for it.